Apparatus for the simultaneous deposition by physical vapor deposition and chemical vapor deposition and method therefor

ABSTRACT

Apparatus and method for the vacuum deposition of at least two different layers of thin film material onto a substrate by two different vacuum deposition processes. Also disclosed is a novel linear applicator for using microwave enhanced CVD to uniformly deposit a thin film of material over an elongated substrate.

REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. pat. application Ser.No. 09/262,515, entitled “Apparatus For The Simultaneous Deposition ByPhysical Vapor Deposition And Chemical Vapor Deposition And MethodTherefor ” by Dotter et al., filed Mar. 4, 1999, which is now issuedU.S. Pat. No. 6,186,090 B1, the disclosure of which is herebyincorporated by reference.

FIELD OF THE INVENTION

This invention relates generally to apparatus for the simultaneousphysical vapor deposition (“PVD”) and chemical vapor deposition (“CVD”)of thin film material onto a substrate, and more particularly, to anovel apparatus for the simultaneous sputtering and microwave chemicalvapor deposition of thin film material onto a substrate, most preferablyan elongated web of substrate material.

BACKGROUND OF THE INVENTION

A variety of products may be fabricated by thin film processes. Examplesof the products that may be fabricated by the deposition of thin filmmaterials include interferometer stacks for optical control and solarcontrol. An example of a solar control product is disclosed in U.S. Pat.No. 5,494,743 to Woodard, et al entitled “ANTIREFLECTION COATINGS”, thedisclosure of which is incorporated herein by reference. Morespecifically, Woodard, et al disclose a polymeric substrate havingantireflective coatings disposed thereon. The anti-reflective coatingsconsist of one or more inorganic metal compounds with indices ofrefraction higher than that of the polymeric substrate.

Thin film materials that are used for optical control an generallycomprised of a series of layers of metals and dielectrics of varyingdielectric constants and indices of refraction. These thin filmmaterials may be used, for example, to reduce glare or reflection. Thinfilm materials may also be used as solar control films for low emissionof infrared radiation in order to reduce the loss of heat.

In the manufacture of thin film materials for optical control, manyinterferometer stacks will have a top layer of silicon dioxide. Anantireflective layer for a single layer of material having an index ofrefraction greater than 1.00 will have an index of refraction equal tothe square root of the index of refraction of the single layer material.The thickness of the material calculated at the center wavelength of thefrequency band at issue, more precisely, the optical thickness is ¼ ofthe wavelength at the center frequency. For example, the human eyegenerally sees light having a wavelength between 4000 Å and 7000 ÅTherefore, the thickness of the optical coating for anti-reflection at5500 Å is about 1375 Å Optical properties including the index ofrefraction and transparency as well as with the mechanical properties ofsilicon dioxide make it the material of choice for anti-reflectivecoatings.

A number of processes are currently utilized to deposit thin filmmaterials, some of which are described in Thin Film Processes. John L.Vossen and Warner Kern, eds., Academic Press, Inc., New York, N.Y.,1978. The fundamentals of chemical vapor deposition are disclosed inChapter III-2 of Thin Film Processes by Warner Kern and Vladimir S. Ban.Chemical vapor deposition, CVD, as a method of forming and depositingmaterial causes the constituents of a gas or vapor phase of a materialto form a product which is deposited on some surface. Therefore, thechemical reaction may be either endothermic or exothermic.

The reactants of a CVD process are the logical result of the stackdesign and are determined by the precursor materials. For example, ifsilicon dioxide (SiO₂) is desired to be deposited, silane (SiH₄) may beoxidized by oxygen (O₂) to yield silicon dioxide as the desired productand a by-product of hydrogen (H₂). Alternatively, silane may bedecomposed to deposit an amorphous silicon alloy material on asubstrate. For example, products may be formed by energizing thereactants to a reaction temperature. The reaction temperature may beachieved by any suitable method known in the art including R.F. glowdischarge and electrical resistive heating. A CVD reaction may occur ina wide range of pressures from above an atmosphere to a less than amillitorr.

Low pressure CVD processes offer substantial advantages over CVDprocesses operating at about atmospheric pressure. The diffusity of agas and the mean free path of gas molecules is inversely related topressure. As the pressure is lowered from about atmospheric pressure to1 torr, the effect is an increase of approximately 2 orders of magnitudein the diffusion constant. Commonly assigned, U.S. Pat. Nos. 4,517,223and 4,504,518 to Ovshinsky, et al both entitled “METHOD OF MAKINGAMORPHOUS SEMICONDUCTOR ALLOYS AND DEVICES USING MICROWAVE ENERGY”, thedisclosures of which are incorporated herein by reference, describedprocesses for the deposition of thin films onto a small area substratein a low pressure, microwave glow discharge plasma. As specificallynoted in these patents, operation in low pressure regimes not onlyeliminates powder and polymeric formations in the plasma, but alsoprovide the most economic mode of plasma deposition.

A low pressure microwave initiated plasma process for depositing aphotoconductive semiconductor thin film on a large area cylindricalsubstrate using a pair of radiative waveguide applicators in a highpower process is disclosed in commonly assigned, U.S. Pat. No. 4,729,341to Fournier, et al for “METHOD AND APPARATUS FOR MAKINGELECTROPHOTOGRAPHIC DEVICES”, the disclosure of which is incorporatedherein by reference. However, the principles of large area depositiondescribed in the '341 patent are limited to cylindrically shapedsubstrates and the teachings provided therein are not directlytransferable to an elongated web of substrate material.

The use of a microwave radiating applicator has been extended tochemical vapor deposition onto an elongated web of substrate material incommonly assigned U.S. Pat. No. 4,893,584 to Doehler, et al for “LARGEAREA MICROWAVE PLASMA APPARATUS”, the disclosure of which isincorporated herein by reference. By optimizing the isolating window towithstand compressive forces, the thickness of the window may beminimized to provide for rapid thermal cooling, whereby the '584 patentachieves a high power density without cracking the window. Furthermore,by maintaining the apparatus of the '584 patent at subatmosphericpressures, it is possible to operate the apparatus at a pressureapproximating that required for operation near the minimum of a modifiedPaschen curve. As disclosed in commonly assigned U.S. Pat. No.4,504,518, a Paschen curve is the voltage needed to sustain a plasma ateach pressure. A modified Paschen curve is related to the power requiredto sustain a plasma at each pressure. The normal operating range isdictated by the minimum of the curve. Additionally, the low pressuresallow for a longer mean free path of travel for the plasma species,thereby contributing to overall plasma uniformity.

In a CVD process, a sufficient proportion of feedstock gases areprovided to achieve a correct stoichiometric deposition of materials. Anexcellent method for chemical vapor deposition is disclosed in commonlyassigned U.S. Pat. No. 5,411,591 to Izu, Dotter, Ovshinsky, and Hasegawaentitled “APPARATUS FOR THE SIMULTANEOUS MICROWAVE DEPOSITION OF THINFILMS IN MULTIPLE DISCRETE ZONES”, the disclosure of which isincorporated by reference herein, Izu, et al disclose an apparatus forthe microwave plasma enhanced chemical vapor deposition of thin filmmaterial onto a web of substrate material utilizing a linear microwaveapplicator. By maintaining the plasma region at subatmosphericpressures, a longer mean free path of travel for the plasma species isavailable, which contributes to the overall plasma uniformity.

In order to maintain a uniform plasma over a much wider substrate, about1 meter or wider, spacing between the windows must be decreased. As thespacing between the windows of the linear applicator decrease, thepotential for shorting increases. It is not possible to maintain aplasma if the linear applicator is prone to shorting. One advantage of aCVD process is the film deposition rate. The product formation rate in aCVD apparatus is related to the flow rate of the feedstock gases. As therate of product formation increases, the deposition rate also increases.So long as enough energy is provided to react the feedstock gases, thedeposition rate is limited by the rate at which non-deposited speciesmay be evacuated from the CVD apparatus. Although a CVD process workswell for many thin film materials, there are many materials which aredesired and cannot be deposited by any known CVD process, such as indiumtin oxide, ITO.

Another known method of depositing thin film material is a PVD (PhysicalVapor Deposition) process. There are a number of PVD processes known inthe art of thin film material deposition, many of which are disclosed inTHIN FILM PROCESSES. J. L. Vossen and W. Kern, eds., Ch. II, AcademicPress, New York, N.Y. 1978.

A common PVD process is sputtering which deposits fine particles from asource material. Although the nomenclature is unintuitive, the source ofthe material to be deposited upon the substrate is called the target.The term “target” evolves from the process of bombarding the sourcematerial with a charged noble gas. The target is affixed to a cathodewhich is a plate having a negative electrical bias. The target faces thesubstrate material which may be grounded, floating, biased, heated,cooled or some combination thereof. An inert reaction gas, typicallyargon, is introduced and ionized to provide a medium for transporting anelectrical charge. The reaction gas may be ionized by a number ofmethods including an anode plate, a positively biased inlet port or bybiasing the substrate itself. The positively charged reaction gas ion isrepelled from the positively charged source and is electricallyattracted to the target plate where the positively charged ion strikesthe target and removes target atoms by momentum transfer. The removedatoms travel toward the substrate where they condense into thin films.

Although a sputtering process generally does not consume gas forpurposes of thin film deposition, it is desirable to flow an inert gas.Flowing the inert gas provides for the removal of impurities which mayotherwise accumulate within the chamber. When flowing the inert gas, apumping scheme should be employed in order to maintain the pressurewithin the sputtering chamber. It is important to maintain an isobariccondition in the vicinity of the sputtering targets. A pressure gradientwill result in a nonuniform bombardment of the sputtering target andconsequently non-uniform film deposition. Generally, the chamberpressure for sputtering processes is 75 millitorr or lower. Low pressuresputtering, where the sputtering chamber pressure is about 10 millitorror less, provides reaction gas ionization far away from the cathodewhere the chance of the electrical charge being lost to the chamberwalls is greatly increased. Therefore, ionization efficiencies are lowand self-sustained discharges cannot be maintained in a planarsputtering process.

Reactive sputtering, a method that may be used to form oxides forexample, is conducted at a very low pressure, about 5 mtorr or less. Thegoal in reactive sputtering is to increase the amount of gas phasechemistry, which will increase the probability of collisions, which maybe achieved by raising the pressure. However, if SiO₂ is to be depositedby DC sputtering for example, a silicon target is used in an atmospherecontaining oxygen. However, oxygen will react with the silicon targetmaterial, forming SiO₂, which is an insulator. A DC current cannot bemaintained in the present example once the silicon target is oxidized;the charged particle will not have an electrical field to move through.

By the addition of a magnetic field to a sputtering process, sputteringcan be maintained at a pressure below 10 millitorr. The mean free pathof a charged particle is increased by the addition of the magneticfield. By applying a magnetic field perpendicular to an electric field,the path of the electron is influenced and becomes perpendicular to boththe magnetic field and the electrical field. A planar magnetronsputtering device, for example, having a plurality of permanent magnetswhich are disposed parallel to one another and oriented with alternatingpolarity on one plane, creates a circular or oval electron path. Withthe addition of an electrical field, the charged particle takes on ahelical path.

The helical path of a charged particle has two advantages: first, thecharged particle is prevented from contacting the chamber walls by thepresence of the magnetic field, thereby increasing low pressureefficiency; and second, by increasing the length of the traveled path,the potential for collision with other particles has increased.

Although sputtering is a common and well-refined practice, it does havesome disadvantages. One of the disadvantages associated with sputteringis the rate of deposition. For example, silicon dioxide can be depositedby both magnetron sputtering and microwave plasma enhanced chemicalvapor deposition. The deposition rate of silicon dioxide for pulsedmagnetron sputtering is 10-20 Å per second while silicon dioxidedeposited by microwave plasma enhanced chemical vapor deposition isdeposited at a rate of 100-200 Å per second, an order of magnitudeimprovement. However, as noted above, there are materials, such as ITO,for which there are no known methods for deposition by chemical vapordeposition.

Thin film materials for the manufacturer of interferometer stacks foroptical and thermal control generally consist of multiple layers ofmaterials having a determined thickness layered upon a substrate. Thematerials and their associated thickness' are collectively referred toas a “stack.” A stack is designed to achieve a particular purpose,whether that purpose be optical control, solar control or any otherdesign objectives sought to be achieved. As mentioned above, manyoptical and solar control stacks have a relatively thick, about 1000 Å,top layer of SiO_(x). If a stack requires at least one layer to besputtered, then one of two alternatives is available, under the currentstate of the art, to produce the top layer of SiO_(x). The firstalternative is to sputter the entire stack. However, because of thesputtering deposition rate of SiO_(x) and the required materialthickness of SiO_(x) for the top layer of the stack, a substantiallylong process time is required to manufacture the stack. Alternatively,all layers except for the top layer of SiO_(x) may be manufactured byPVD and then the entire roll of sputtered substrate material istransported to a machine for CVD of the 1000 Å layer of SiO_(x).Although both of these approaches create the desired final product, thetime required to manufacture the stack is substantially long, resultingin higher production costs and reduced efficiency. Furthermore, if thecoating is intended for a wide material, about 1 meter, such as a windowfor a commercial building, the state of the art does not provide a meansfor depositing a uniform layer of material by CVD.

Therefore, there exists a need in the art for an apparatus whichsubstantially reduces the amount of time required to manufacture aproduct consisting of multiple layers of thin film material deposited ona substrate by including a PVD process and CVD process in singlemachine.

Furthermore, there exists a need in the art for a CVD process that iscapable of depositing a uniform layer of material onto a widenedsubstrate.

SUMMARY OF THE INVENTION

There is disclosed herein novel apparatus for the deposition of thinfilm material upon a substrate. The apparatus comprises a depositionchamber and a pump for evacuating the interior of the chamber. Asubstrate is operatively disposed within the chamber, and the substrateis movable from a first to at least a second station for the depositionof different layers thereupon. The apparatus further comprises a firstmeans for depositing the first layer of thin film material onto thesubstrate and a second means for depositing the second layer of thinfilm material atop the first layer. The first and second means areadapted to deposit the layers by two different deposition processesselected from the group consisting of a PVD process and a CVD process.

The PVD process is selected from the group consisting of D.C.sputtering, D.C. magnetron sputtering, R.F. sputtering, R.F. magnetronsputtering, reactive sputtering, evaporative deposition, reactiveevaporative deposition, and plasma arc deposition; and the CVD processis selected from the group consisting of thermal CVD, hot wire CVD,PECVD, MPECVD, DCPECVD, RFPECVD, WMPECVD, and ECR (electron cyclotronresonance). Material provided by each of at least two differentdeposition processes is confined within a distinct and substantiallyisolated deposition region. Each deposition region is isolated by aconfinement system. The PVD process and CVD process operate atsubstantially the same pressure. The pressure difference between each ofthe different processes is no greater than an order of magnitude.

There is also disclosed herein an apparatus for the deposition of thinfilm material onto a substrate at subatmospheric pressure. The apparatuscomprises a deposition chamber, at least one PVD means for depositingthin film material upon a substrate operatively disposed within thedeposition chamber within a PVD region; and at least one CVD means fordepositing thin film material upon a substrate operatively disposedwithin the deposition chamber within a CVD region.

A plurality of confinement systems are disposed within the depositionchamber. The PVD region is substantially isolated by at least one of theconfinement systems, and a CVD region is substantially isolated by atleast another one of the confinement systems is at least partiallydefined by another one of the confinement systems, whereby non-depositedspecies from the respective deposition regions are prevented fromcontaminating adjacent deposition regions.

The PVD means may be a sputtering device disposed within the depositionchamber. The sputtering device comprises a cathode within the depositionchamber and at least one target secured to the cathode. The targetconsists of material to be deposited onto the substrate. The CVD meansmay be a microwave plasma enhanced chemical vapor deposition (“MPECVD”)device comprising an applicator enclosure and a linear applicator havinga first end and a second end. The linear applicator has at least oneaperture and is disposed within the applicator enclosure so as toisolate the linear applicator from the deposition chamber. A wave guidecommunicating with the first end of the linear applicator directsmicrowave energy from a microwave source communicating with the waveguide. The aperture is adapted to generate a uniform plasma from themicrowave energy dispersed within the CVD region of said depositionchamber.

There is also disclosed herein a widened microwave device comprising anapplicator enclosure and a widened microwave linear applicator disposedwithin the applicator enclosure. The widened linear applicator has afirst applicator half and a second applicator half, each of the firstand second applicator halves having a first end and second end. At leastone aperture is disposed within each of said first and second applicatorhalves. The second end of the first applicator half is communicatingwith the second end of the second applicator half. A first wave guide iscommunicating with the first end of the first applicator half, and asecond wave guide is communicating with the first end of the secondapplicator half. A microwave source is communicating with the first andsecond wave guides, whereby microwave energy produced by the microwavesource is guided to the first and second applicator halves. The aperturedisposed within each of the first and second applicator halves allowingmicrowave energy to form a CVD plasma when said device is operativelydisposed within an evacuated deposition chamber process gas isintroduced therein.

There is also disclosed a method for fabricating an interferometer stackdeposited upon a substrate, the stack having at least two layers, eachlayer formed by a different deposition process selected from the groupconsisting of a PVD process and a CVD process, comprising the steps of:providing a deposition chamber; evacuating the deposition chamber to subatmospheric pressure; providing a substrate within the depositionchamber; depositing a first layer of material by a first processselected from a PVD process or a CVD process onto the substrate; anddepositing a second layer of material by the other of the PVD process orCVD process atop the first deposited layer of the substrate. Theinterferometer stack may be a multi-layer selective solar controlcoating for optical substrates formed from at least one of moistureresistant dielectric materials and semiconductor materials. Thedielectric material is one or more compounds selected from the groupconsisting of silicon nitride, silicon oxide, titanium oxide, siliconoxynitride, alloys of these materials with carbon and diamond-likecarbon. The semiconductor material is one or more compounds selectedfrom the group consisting of silicon carbide, silicon, doped silicon,germanium, doped germanium and germanium carbide.

These and other objects and advantages of the present invention willbecome apparent from the detailed description, the drawings and claimswhich follow hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view, partially in cross-section, of a firstembodiment of the apparatus according to the teachings of the presentinvention, the cross-section taken through the vacuum depositionchamber, showing the substrate in phantom in order to reveal theoperative elements disposed within the single chamber. This figureillustrates a substrate traveling linearly from a PVD station to a CVDstation;

FIG. 2 is a cross-sectional view of a second embodiment of the apparatusaccording to the teachings of the present invention in which a PVDregion and a CVD region are included within a vacuum deposition chamberand the substrate follows a serpentine path through the vacuumdeposition chamber;

FIG. 3 is a cross-sectional view of a third embodiment of the apparatusaccording to the teachings of the present invention employing aplurality of confinement systems with the substrate following an arcuatepath adjacent to the plurality of confinement systems and in contactwith a chill wheel;

FIG. 4 is a schematic view of an embodiment of a RVD device, morespecifically, a magnetron sputtering device illustrating the depositionof the reaction gas inlet manifolds;

FIG. 5 is a cross-sectional view of a first embodiment of a CVD device,more specifically, a plasma enhanced chemical vapor deposition device,illustrating the operative elements disposed within the confinementsystem and including the feed stock gas inlet manifold, feed stock gasexhaust manifold, and linear microwave applicator of the instantinvention;

FIG. 6 is an illustration of an embodiment of a microwave enhancedchemical vapor deposition system of the instant invention with thesubstrate operatively located within the vacuum deposition chamber, anddisclosing operative elements including: a power supply, microwavesource, three port isolator, tuner, linear microwave applicator and amicrowave isolation enclosure;

FIG. 7 is an isometric view of an embodiment of a linear microwaveapplicator;

FIG. 8 is an illustration of a first embodiment of the widened microwaveplasma enhanced CVD device; and

FIG. 9 is an isometric view of an embodiment of the widened linearmicrowave applicator of the instant invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to an apparatus for the simultaneousdeposition of thin film material by a Physical Vapor Deposition (“PVD”)process and/or a Chemical Vapor Deposition (“CVD”) process onto asubstrate. Although one skilled in the art would recognize the processesthat are included in the groups referred to as a PVD processes and a CVDprocesses, and not intending to be exhaustive, PVD processes include:D.C. sputtering, D.C. magnetron sputtering, R.F. sputtering, R.F.magnetron sputtering, reactive sputtering, evaporative deposition,reactive evaporative deposition, and plasma arc deposition; and CVDprocesses include: thermal CVD, hot wire CVD, plasma enhanced chemicalvapor deposition (“PECVD”), microwave plasma enhanced chemical vapordeposition (“MPECVD”), D.C. PECVD (“DCPECVD”), R.F. PECVD (“RFPECVD”),widened MPECVD (“VVMPECVD”) and electron cyclotron resonance (“ECR”).

Pursuant to the subject invention, at least two different processesoperate within a single vacuum deposition chamber. The processes may beselected from the PVD group, the CVD group, or any combination thereof.The processes preferably operate at substantially the same operatingpressure, generally the pressure difference between each of thedifferent processes is no greater than an order of magnitude. Theoperation of each of at least two different processes is made possibleby substantially confining species formed as a result of each processwithin a substantially isolated deposition region. The deposition regionis that portion of the deposition chamber where material from either aPVD process or CVD process is deposited upon a substrate.

The threat of cross contamination of materials, whether they be excitedspecies, precursor gasses, products of a CVD process or products of aPVD process, cannot be tolerated. By preventing cross contamination,combinations of PVD or CVD processes may be functionally deployed withina single deposition chamber, resulting in increased efficiency andreduced production costs. Cross contamination is prevented by aconfinement system. The confinement system may be particle vectorconfinement, gas gate confinement, or the like, depending on theoperating pressure required. Previously, if a stack design called formaterials that must have been deposited by at least two differentprocesses that could not be disposed in the same deposition chamberbecause of cross contamination concerns, the processes would have to beexecuted separately.

The present invention contemplates a substrate movable from a first ofat least two deposition stations to a second deposition station.However, the principles of the present invention may be applied to astationary substrate operatively disposed adjacent to each of at leasttwo deposition stations. A deposition station is a spatially discretedeposition location where a deposition process is executed.

In the exemplary embodiment, an apparatus is disclosed incorporating aPVD device and a CVD device, where cross contamination is prevented byparticle vector confinement. One specific PVD device disclosed is amagnetron sputtering device, and one specific CVD device disclosed is anMPECVD device. It should be noted that any suitable CVD device orprocess may be substituted for the MPECVD device. Likewise, it shouldalso be note that any suitable PVD device or process may be substitutedfor magnetron sputtering. The sputtering and microwave plasma enhancedchemical vapor deposition processes occur within an evacuated chamber atsubatmospheric pressure. By providing a PECVD and sputtering within thesame deposition chamber, the advantages of each process may be harvestedwith an increased efficiency over the prior art. This exemplaryembodiment of the apparatus of the present invention combines the highrate of material deposition provided by PECVD in concert with thevariety of materials that may be deposited by sputtering.

Referring now to FIG. 1, a schematic cross-sectional illustration of afirst embodiment of apparatus 10 for simultaneous deposition of one ormore thin film materials onto a substrate material by a CVD process andPVD process is shown.

The apparatus 10 includes a vacuum deposition chamber 20, the walls ofwhich are preferably formed of a durable, corrosion resistant materialsuch as stainless steel. Disposed within the deposition chamber 20 is aPVD device 50 and a CVD device 60. Material provided by the PVD device50 is deposited upon a substrate 30 within a PVD deposition region 55.Likewise, material provided by the CVD device 60 is deposited upon thesubstrate 30 within a CVD deposition region 65. Substrate 30 is disposedwithin the deposition chamber 20 and is movable from at least a firstdeposition station 70 to a second deposition station 80 for thedeposition of different layers thereon. Although two layers may consistof the same material, if the layers are deposited at discrete locationswithin the chamber 20, they are different layers for purposes of thisinvention. Different layers also refers to layers deposited by at leasttwo different means selected from the group consisting of a PVD processand a CVD process. A PVD process or a CVD process may be provided at thefirst deposition station 70. Likewise, second deposition station 80 mayprovide either a PVD process or a CVD process. A plurality ofconfinement chambers 90 are disposed within the deposition chamber 20.Each of the plurality of confinement chambers 90 has at least oneaperture 95. Each of the PVD region 55 and the CVD region 65 areisolated by one of a plurality of confinement systems. Each of the PVDdevice 50 and the CVD device 60 may be disposed within, partiallydisposed within, or in communication with one of the plurality ofconfinement chambers 90. The substrate 30 is disposed in close proximityto the aperture 95 of each confinement chamber 90 at least partiallydefining a PVD region 55 and a CVD region 65, thereby further definingthe PVD region 55 and CVD region 65.

One or more glow bars 40 may be disposed within the deposition chamber20. The addition of one or more glow bars 40 assist in the adherence ofthin film materials to the substrate 30. The substrate 30 may be anelongated web of substrate material that is adapted for deposition ofthin film materials. A vessel pump-down port 350 is adapted to be incommunication with the deposition chamber 20 and is also incommunication with a pump farm 360.

Referring now to FIG. 2, a schematic cross-sectional view of a secondembodiment of the apparatus 10 according to the teachings of the presentinvention is shown. One or more guide rollers 340 may be employed todirect the substrate 30 within the vacuum deposition chamber 20. In theimmediate embodiment of the present invention, a PVD device 50 and CVDdevice 60 are each isolated by a confinement system, and morespecifically, by one of a plurality of confinement chambers 90. Each ofa PVD region 55 and CVD region 65 are defined by one of the plurality ofconfinement chambers 90, each confinement chamber 90 defining either aPVD region 55 or CVD region 65 has an aperture 95 where the substrate 30subtends each aperture 95.

Although a PVD device 50 precedes a CVD device 60 in the order ofdeposition as disclosed in the present embodiment of apparatus 10, anycombination of a CVD device 60 and/or a PVD device 50 may be employed.The order of deposition within the deposition chamber 20 is governed bythe design of the interferometer stack. As an example, if the design ofthe stack requires that a first layer, the layer closest to thesubstrate 30, have a composition that is more efficiently deposited by aPVD process, then a PVD device 50 will deposit a layer of material uponthe substrate 30. The flexibility of the present invention allowsseveral PVD and/or CVD processes to operate within the depositionchamber 10, in any desired order. Thus, it should become apparent tothose skilled in the art that the novel teachings of the presentinvention provide substantial advantages over the prior art.

Referring now to FIG. 3, a schematic cross-sectional view of a thirdembodiment of the present invention is shown. In the present embodiment,the substrate 30 is drawn from a payoff reel 310 and through thedeposition chamber 20 by a take-up reel 330. A chill roller 320 isdisposed within the deposition chamber 20 in the instant embodiment ofthe present invention. A plurality of guide rollers 340 are disposedwithin the vacuum deposition chamber 20 to guide the web of substratematerial and take up any slack or relieve stress upon the substratematerial 30 as the substrate material 30 passes through the vacuumdeposition chamber 20.

After the substrate 30 has traveled past the PVD region 55, thesubstrate 30 continues to travel through the deposition chamber 20 tothe CVD region 65 where a CVD process deposits thin film materials ontothe substrate 30. FIG. 3 shows the apparatus 10 of the present inventionhaving two confinement chambers 90, each having a sputtering device 100disposed therein, and two other confinement chambers 90, each having amicrowave enhanced chemical vapor deposition (“MPECVD”) device 110disposed therein.

Referring now to FIG. 4, a cross-sectional view of a confinement chamber90 containing a sputtering device 100 is shown. The sputtering device100 includes target 150 attached to a cathode 140. The target 150 isactually the source of the material to be deposited, for example ITO. Aplurality of magnets 160 are disposed within the deposition chamber 20and proximal to the cathode 140. Although the presence of the magnets160 in this particular embodiment of the present invention reveals thisis a magnetron sputtering device, it should be noted that any methodknown in the art for a subatmospheric pressure PVD process may beemployed in the instant invention. A reaction gas inlet manifold 120 isadapted to provide reaction gas within the confinement chamber 90containing the PVD region. One or more reaction gas exhaust manifolds130 are provided to be in communication with one of the plurality ofconfinement chambers 90.

A reaction gas, for example argon, is introduced to the confinementchamber 90 by the reaction gas inlet manifold 120. A steady flow of thereaction gas is provided to maintain stoichiometry during the sputteringprocess. Referring now also to FIG. 3, the cathode 140 has a negativeelectrical charge which may be in the form of a DC current or highfrequency alternating current, also known as R.F. By the addition of amagnetic field, an increase in the traveled path of electrons within theplasma is achieved in order to sustain a plasma charge. Low pressuresputtering devices typically employ a magnetic field because theparticle density within the plasma region is very low, i.e. in themillitorr regime. Otherwise, electrons which leave the cathode 140 maystrike the chamber 20 walls or any other surface and discharge resultingin a lack of efficiency and ultimately, plasma failure. The magneticfield forces the electrons to travel in a spiral path therebymagnetically confining the electrons. The deposition chamber 20 may havea positive electrical bias. Once an electron strikes a reaction gasatom, an electron will be stripped, and a positive charge on thereaction gas atom will result, and is consequently propelled toward anegatively charged surface, a negatively charged target 150 for example.A collision with the target 150 will cause a small portion of the targetmaterial 150 to be dislocated and deposited upon the substrate 30. Argongas is commonly used as a reaction gas for sputtering, however, oneskilled in the art would recognize that other reaction gases may besubstituted.

Referring now also to FIG. 1, the pressure within the confinementchamber 90 at least partially defining the PVD region 55 has a pressurebetween about 1 millitorr and 10 millitorr, preferably operating at apressure between 2 and 3 millitorr. The pressure within the confinementchamber 90, at least partially defining the PVD region 55, is achievedby employing a vacuum source in communication with the reaction gasexhaust manifold 130. As few as one vacuum source may be employed toachieve the desired pressures throughout the chamber 20. The vacuumsource utilized in the preferred embodiment of present invention isdriven by one or more diffusion pumps, however, one skilled in the artwould immediately recognize that suitable substitutes for diffusionpumps may be employed.

Referring now to FIG. 5, a cross-sectional view of another confinementchamber 90, at least partially defining a CVD region 65, is shown. Inthe present embodiment, the CVD device 60 is disposed within theconfinement chamber 90 at least partially defining the CVD region 65.The CVD device 60 includes a linear microwave applicator 250, which isdisposed within a confinement chamber 90. A feedstock gas inlet manifold180 may be disposed within the confinement chamber 90, or, alternativelythe feed stock gas inlet manifold 180 may be physically located outsideof, but in communication with the confinement chamber 90 at leastpartially defining the CVD region 65. An example of an excellent linearmicrowave applicator may be found in commonly assigned U.S. Pat. No.5,411,591 to Izu, et al for “APPARATUS FOR THE SIMULTANEOUS MICROWAVEDEPOSITION OF THIN FILMS IN MULTIPLE DISCRETE ZONES,” incorporatedherein by reference. Although a plasma enhanced chemical vapordeposition device is disclosed in the immediate example, it shouldbecome readily apparent to one skilled in the art that any chemicalvapor deposition process capable of operating at the pressures disclosedherein would be a suitable substitute. The MPECVD device disclosedherein operates between about 1 to 10 millitorr, and preferably, between5 to 10 millitorr. The mass flow rate of feedstock gases and thecapacity of the vacuum source primarily dictate the pressure within theconfinement chamber 90 partially defining the CVD region.

Referring now also to FIG. 3, in one embodiment of the presentinvention, the chamber 20 has a background pressure, that is a pressurewithin the chamber 20 not occupied by the CVD region 65 or PVD region55, below that of either the CVD region 65 or PVD region 55 in order toprevent cross contamination. In the event species should escape fromeither the PVD region 55 or CVD region 65, the species will be drawn toan area within the chamber 20 not occupied by the CVD region 65 or PVDregion 55. By employing a flow restriction device such as chevron, gasflow may be selectively restricted to achieve the desired pressures withas few as one vacuum source. In another embodiment of the presentinvention, one vacuum source may be assigned to facilitate each of thechamber background pressure, the PVD region 55 pressure, and the CVDregion 65 pressure.

Referring again now to FIG. 5, the feedstock gas inlet manifold 180provides the feedstock gases which are the reactants for the CVDprocess. The feedstock gases are optimized to provide the correctcomposition of the desired deposition material. For example, if silicondioxide is desired, a mixture of about 200 sccm SiH₄ (silane), 600 sccmO₂ and 150 sccm Ar is introduced into the CVD region 65. Thisoxygen-rich mixture is so provided in order to maximize the reaction ofsilane, resulting in a higher percentage of silicon dioxide depositionand a lower presence of Si-H bonds in the deposited films. Thedeposition rate in a CVD process is limited only by the mass flow rateof the feedstock gases provided to the CVD region. In order tocapitalize on the advantages of low pressure CVD, the pressure withinthe confinement chamber 90 must be maintained below about 10 millitorr.The limitation on the deposition rate of low pressure CVD processes suchas MPECVD is limited by the throughput of the vacuum source.

The microwave device 110 radiates microwave energy into the feedstockgas stream provided by the feedstock gas inlet manifold 180. As thefeedstock gases are radiated with microwave energy, a plasma is formedwithin the CVD region 65, causing the feedstock gases to react and formthe material to be deposited upon the substrate 30. A plasma sustaininggas, such as argon, may be used to assist in the maintenance of theplasma. As the precursor gases flow through the CVD region 65, thenon-deposited species and any plasma sustaining gas is drawn out of theCVD region 65 by the feed stock gas exhaust manifold 190. Referring alsonow to FIG. 3, a pump out region 170 may be disposed within thedeposition chamber 20 along the path of the substrate 30. In the instantembodiment, the pump out region 170 comprises a vacant confinementchamber 90. The pump-out region 170 may be disposed adjacent to the CVDregion 65 and employed to be a common collector of non-deposited speciesand any plasma sustaining gas. A feedstock gas exhaust manifold 190 isshown in communication with the pump-out region 170, so as to form aconduit between the pump-out region 170 and a vacuum source. One skilledin the art would immediately recognize the feedstock gas exhaustmanifold 190 may be disposed within or adjacent to the confinementchamber 90 containing the CVD region 65 without including pumpout region170.

Referring now to FIG. 6, an illustration of an embodiment of a microwaveenhanced chemical vapor deposition device 110 is shown. The microwavedevice 110 includes a power supply 200 which is coupled to a microwavesource 210 by any method known in the art in order to provide a sourceof electrical power to the microwave source 210. The microwave source210 may be a magnetron head which is commonly known in the art. Onevariety of a magnetron head utilizes a filament charged with a very highvoltage (at least 1 kV) disposed in the center of a thick walled vacuumchamber. The vacuum chamber of the magnetron head has a magnetic fieldapplied so that the field lines run parallel to the long axis of thevacuum chamber and also parallel to the charged filament. The magneticfield causes electrons from the filament to begin to orbit the filament,tangential to the interior chamber wall which is cylindrical in shape. Aplurality of cavities are in communication with the magnetron chamberhousing the filament. The cavities have their own frequency and rhythm,causing the electrons to bunch near each cavity as they orbit thefilament within the magnetron chamber. The electrons continue to cyclewithin the magnetron chamber until they reach an operating frequency ofabout 2.45 gigahertz. An antennae disposed in one of the cavities isaffected by the cycling electrons and is adapted to transmit highfrequency electrical energy toward a target Microwaves are emitted fromthe antennae into a wave guide 260 which guides the microwaves through athree port isolator 220 and then to a tuner 230. The three port isolator220 restricts microwave travel to a single direction. Any microwaveswhich are reflected back toward the three port isolator 220 areredirected by the three port isolator 220, for example to a water load.The tuner 230 is a load matching device adapted to reduce reflectedpower. The microwaves continue to travel through the wave guide 260 andinto a linear microwave applicator 250 which evenly distributes themicrowave energy into the CVD region. The linear microwave applicator250 may be a separate component from the wave guide 260, or the waveguide 260 and linear applicator 250 may be an integrated component.

Referring now also to FIG. 7, an isometric view of an embodiment of thelinear microwave applicator 250 is shown. The applicator 250 is agenerally rectangular shaped channel having a plurality of aperturesdisposed along one side. FIG. 7 discloses the linear applicator 250having a first end 251, a second end 252, and a series of apertures 253through 258 spaced about 1 wavelength apart with respect to eachaperture's 253 through 258 center. The microwave energy enters at thefirst end 251 adjacent to aperture 253. The microwave energy “leaks”from the linear applicator through apertures 253 through 258.

As the microwave energy leaks, the microwave power within the applicatoris decreased in intensity. For example, if 16% of the microwave energywere permitted to leak from aperture 253, the power of the microwavesignal would be reduced to 84% of the original power. By permitting themicrowave energy to leak in a substantially uniform manner, a uniformplasma may be created within CVD region 65. It should be noted thatalthough the embodiment of linear applicator 250 discloses sixapertures, 253 through 258, as substantially rectangular, it should benoted that various and variable aperture geometries may be employed toachieve a uniform microwave field within the CVD region 65. It shouldalso be noted that adjustment of the leak of apertures 253 through 258is strictly empirical and that tuning is required in order to achieve auniform microwave field within the CVD region 65. It should further benoted that although six apertures have been disclosed in this embodimentof the present invention as in FIG. 7, any suitable number of aperturesmay be employed to achieve the desired result.

The plurality of apertures 253 through 258 are spaced at approximately 1wavelength apart in order to prevent adjacent microwave fields fromcanceling one another. The microwave device 110 is designed to provide atraveling wave, so as to avoid problems that accompany a standing wave.The plasma may be stabilized through empirical methods only. The stateof the art does not provide adequate information that would enable thoseskilled in the art to model the present relationship involving thisphase dependent absorption.

Returning now to FIG. 6, the microwave device 110 further includes amicrowave applicator enclosure 240 which prevents particles within theCVD region 65 from contaminating the linear applicator 250. Themicrowave applicator enclosure 240 is preferably fabricated from adielectric material which is substantially transparent to microwaveenergy. A preferred material is quartz, however, it should be apparentto those skilled in the art that other suitable materials may besubstituted for quartz. The microwave applicator enclosure 240 may haveone open end whereby the linear applicator 250 is inserted into themicrowave applicator enclosure 240. The enclosure 240 is typically, butnot necessarily, at about atmospheric pressure. Also, the applicatorenclosure 240 may be cooled by a liquid or any other suitable coolingmeans known in the art. Additionally, the microwave applicator enclosure240 may have a second open end and protrude through the vacuumdeposition chamber 20 at both ends. For strength purposes, the microwaveapplicator enclosure 240 should have a generally cylindrical, orgenerally curved shape. The microwave applicator enclosure 240 may besealed at one end with an end cap 270 formed of the same material as themicrowave isolation enclosure 240 and may be securely attached to thevacuum deposition chamber 20 by a retaining cap 290 and retaining rods280. If desired, the microwave applicator enclosure 240 may also takethe form of a test tube, eliminating the end cap 270. One or more seals300 may be employed to prevent air leakage where the microwaveapplicator enclosure 240 penetrates the vacuum deposition chamber 20.

Referring now again to FIG. 5 and FIG. 3, as previously mentioned, themicrowave energy from the microwave device 110 causes the feedstockgases to react and form the products which are deposited upon thesubstrate 30. The microwave energy provides a high density of freeradicals, compared to the more conventional density generated by R.F.,which results in higher deposition rates and nearly 100% utilization ofthe feedstock gases. Additionally, the low pressures create a longermean free path of travel for the excited species, contributing tooverall plasma uniformity. Another benefit to operating atsubatmospheric pressures is the quality of the materials which aredeposited. Operation in low pressure regimes eliminates powder andpolymeric formations in the plasma while providing the most economicmode of plasma deposition.

Each deposition region within deposition chamber 20 is isolated by aconfinement system. In a pressure regime of about 1 millitorr to 10millitorr, the behavior of gas molecules falls between laminar flow andmolecular flow. Laminar flow is characterized by a Newtonian response ofthe fluid to some force. That is, the gas molecules acting in concertare compressible, have a density, viscosity, and when in motion arecharacterized by a boundary layer flow field. In a molecular regime, gasmolecules move independently within a volume; a change in motion, orvector, is a result of a collision. In the molecular regime, a gasmolecule will continue in motion until the molecule strikes some surfaceor another gas molecule, whereby the trajectory of the gas molecule isaltered.

The transition regime between molecular flow and laminar flow is knownas the Knudsen regime, characterized by a hybrid behavior consisting ofqualities of both molecular and Newtonian flow. The mass flow rate for aKnudsen regime gas is described by the equation F=CΔP where F is themass flow rate of the gas, C is conductance and ΔP is a pressure dropacross some restriction from pressure P1 to pressure P2, where ΔP is thedifference of P1 and P2. By operating in the Knudsen gas regime, thebest of both worlds is available in that a plasma may be sustainedwithin this pressure while the gas exhibits molecular behavior.

In the preferred embodiment, each one of the confinement chambers 90have at least one aperture 95. The substrate 30 is in close proximity tothe aperture 95 of each confinement chambers 90 at least partiallydefining a PVD region 55 or a CVD region 65. The substrate 30 being inclose proximity to the aperture 95 of each confinement chamber 90further defines a PVD region 55 and/or a CVD region 65.

Known in the art are various methods for confining species within aregion. A gap between substrate 30 and confinement chamber 90 isprovided so as to be large enough to account for any tolerances that maylead to contact between the confinement chamber 90 and substrate 30.This gap is minimized to confine the matter within each confinementchamber 90 without contacting the substrate 30. In order for the gasmolecules to escape from the PVD region 55 or CVD region 65, the gasmolecule must be traveling in a path nearly parallel to the substrate30. Since the gas flow is not introduced along and parallel to thesubstrate 30 surface, the possibility that a gas molecule will escape inthis manner is very close to impossible, this technique is referred toherein as particle vector confinement, and is commonly used in a deviceknow in the art as a chevron. Therefore, any non-deposited specieswithin a PVD region 55 or CVD region 65 will be removed from theconfinement chamber 90 by either the reaction gas exhaust manifold 130in the case of a PVD process or the feedstock gas exhaust manifold 190in the case of a CVD process. Particle vector confinement preventspotentially hazardous silane molecules from traveling to the PVD region55 where the silane molecules may react with the target 150 resulting incontamination.

Alternatively, cross contamination may be prevented at pressures abovethe Knudsen regime by incorporating gas gate confinement. By takingadvantage of a fluids Newtonian behavior, non-deposited species may beconfined by flowing a gas, an inert gas is typical, but not alwaysnecessary, between two deposition regions. One method of gas gateconfinement is disclosed in commonly assigned U.S. Pat. No. 4,462,333 toNath, et al for “PROCESS GAS INTRODUCTION, CONFINEMENT AND EVACUATIONSYSTEM FOR GLOW DISCHARGE DEPOSITION APPARATUS”, the disclosure of whichis incorporated by reference herein. The gas may flow between two PVDregions 55, two CVD regions 65, or any combination thereof. Byintroducing gas at a higher pressure, or by creating a pressure drop,the particle flow within a PVD region 55 or a CVD region 65 may begoverned.

The present invention contemplates that it may be necessary to confineas few as one deposition region. In the event non-deposited species fromone deposition region are benign to any other deposition regions withinthe deposition chamber 20, confinement would not be required. Eachdeposition region may be isolated by providing a confinement system.Therefore, each of at least two different processes selected from thegroup consisting of a PVD process and a CVD process may provide thinfilm deposition within the same chamber 20 without being subject tocross contamination.

A widened microwave plasma enhanced chemical vapor deposition(“WMPECVD”) device 400, as illustrated in FIG. 8, may be substituted forMPECVD device 110 in order to increase the desired width of depositionof a chemical vapor deposition process. The WMPECVD device 400 includesa microwave applicator enclosure 410 and a widened microwave linearapplicator 420. Referring now also to FIG. 9, the widened microwavelinear applicator 420 has a first end 421 and a second end 422. A firstapplicator half 430 and a second applicator half 440 are in closeproximity to form the widened applicator 420. The first applicator half430 has a first end 431 and a second end 432, and a plurality ofapertures 433 through 438 disposed therein. Similarly, the secondapplicator half 440 has a first end 441 and a second end 442, and aplurality of apertures 443 through 448 disposed therein.

It should be noted that although the embodiment of the widened linearapplicator 420 discloses six apertures in each of first applicator half430 and second applicator half 440, as substantially rectangular, itshould be noted that various and variable aperture geometries may beemployed to achieve a uniform microwave field. It should also be notedthat adjustment of the leak of apertures 433 through 438, and 443through 448, is strictly empirical and that tuning will be required inorder to achieve a uniform microwave field within the CVD region 65. Itshould further be noted that although six apertures have been disclosedin each of first applicator half 430 and second applicator half 440 inthis embodiment of the present invention as in FIG. 9, any suitablenumber of apertures may be employed to achieve the desired result.

The second end 432 of the first applicator half 430 is adjacent to thesecond end 442 of the second applicator half 440. The widened microwavelinear applicator 420 is disposed within the microwave applicatorenclosure 410 to prevent particles from contacting the widened microwavelinear applicator 420.

The WMPECVD device 400 further includes a first wave guide 450 and asecond wave guide 460. The first wave guide 450 is in communication withthe first end 431 of the first applicator half 430, the second waveguide 460 is in communication with the first end 441 of the secondapplicator half 440. A microwave source 470 is in communication with thefirst wave guide 450 and second wave guide 460, whereby microwave energyproduced by the microwave source 470 is guided to the first applicatorhalf 430 and second applicator half 440. At least one aperture isdisposed within a side of each of the first applicator half 430 andsecond applicator half 440, which allows microwave energy provided bythe microwave source 470 to penetrate the CVD region 65. Each of thefirst applicator half 430 and second applicator half 440 may be aseparate component from the first wave guide 450 and second wave guide460, respectively, or integrated components.

A power supply 500 is suitably coupled to the microwave source 470 byany method known in the art. An example of a microwave source is amagnetron head, as disclosed above. The microwave source 470 may becoupled to a microwave splitter 540 in order to distribute microwaveenergy emitted from the microwave source 470. By distributing themicrowave energy from the microwave source 470, only one microwavesource 470 needs to be provided. Alternatively, two microwave sources(not shown), each of which may be in communication with one of the firstand second wave guide, 450 and 460 respectively, without incorporatingthe splitter 540 in order to accomplish the same result.

At least one shorting screw 530 may be disposed between the firstapplicator half 430 and the second applicator half 440 so as to preventmicrowave energy from traveling from the first applicator half 430 tothe second applicator half 440 and alternatively to prevent microwaveenergy from the second applicator half 440 to travel to the firstapplicator half 430. Shorting screw 530 provides a shield to, anddirects excess microwave energy away from the microwave source 470 andwidened linear applicator 420. The first waveguide 450 may be incommunication with a first tuner 550 and the second waveguide 460 may bein communication with a second tuner 560. A first three port isolator510 and second three port isolator 520 may be in communication with thesplitter 540. First and second three port isolator 510, 520 function ina manner similar to three port isolator 220 disclosed above. Three portisolator 510 may be in communication with a first tuner 550 and secondthree port isolator 520 may be in communication with the second tuner560. The tuners 550, 560 control the amount of power provided forchemical vapor deposition.

The widened microwave device 400 of the present invention provides asolution to shorting problems which have been experienced whenattempting to deposit material upon a substrate that is 1 meter orwider. In order to provide the required amount of microwave energy tothe widened microwave linear applicator 420, convention dictates theapertures disposed within the linear applicator must become very narrow.A narrow aperture in a linear applicator is commonly susceptible toshorting problems rendering the device impractical. However, thisobstacle has been overcome by the widened microwave applicator 420 ofthe present invention. Applying the teachings the widened microwaveapplicator 420 of the present invention, a linear applicator of up toabout 120 centimeters long or longer may be achieved.

As shown in FIG. 9, the first applicator half 430 and second applicatorhalf 440 are disclosed in an isometric view. The first applicator half430 is essentially a mirror image of the second applicator half 440.Apertures 433 through 438 ascend in size with respect to the firstapplicator half 430, and apertures 443 through 448 descend in sizeregarding the second applicator half 440. Therefore, it is possible tocreate a uniform plasma while avoiding unwanted arcing by providingmicrowave energy at each of the first end 421 and the second end 422 ofthe widened microwave applicator 420.

An interferometer stack may be fabricated by applying the teachings setforth herein. A stack having at least two layers may be fabricated,wherein each of at least two layers are formed by a different depositionprocess selected from PVD means and/or CVD means. As set forth above,the processes that are included under the group referred to as PVDprocesses and CVD processes, not intending to be exclusive, PVDprocesses include: D.C. sputtering, D.C. magnetron sputtering, R.F.sputtering, R.F. magnetron sputtering, reactive sputtering, evaporativedeposition, reactive evaporative deposition, and plasma arc deposition;and CVD processes include: thermal CVD, hot wire CVD, plasma enhancedchemical vapor deposition (“PECVD”), microwave plasma enhanced chemicalvapor deposition (“MPECVD”), D.C. PECVD (“DCPECVD”), R.F. PECVD(“RFPECVD”), widened MPECVD (“WMPECVD”), and electron cyclotronresonance (“ECR”).

By providing the PVD means and/or CVD means within the depositionchamber while preventing cross contamination when necessary, a stackhaving at least two layers may be fabricated, where at least twodifferent processes provide material to be deposited upon the substrate.The deposition chamber is evacuated to a subatmospheric pressure. Asubstrate is provided to receive materials thereon. PVD means and/or CVDmeans are provided within the deposition chamber.

A first process is provided which has been selected from the groupconsisting of PVD means and/or CVD means. A layer of material providedby the first process is deposited onto the substrate. A second differentprocess is provided which has been selected from the group consisting ofPVD means and/or CVD means. Another layer of material is then depositedupon the substrate.

EXAMPLE

The first step in fabricating an interferometer stack is to provide asubstrate for receiving deposition thin film materials. A roll ofsubstrate material is provided on a pay-off reel disposed within thedeposition chamber of the apparatus of the present invention. Thesubstrate is wound through the deposition chamber, guided by a pluralityof guide rollers, to a take-up reel provided within the depositionchamber. The substrate is in contact with a chill wheel to cool thesubstrate, as the processes operating within the deposition chambercreate a significant amount of heat. The substrate passes by a pluralityof glow bars as the substrate is drawn off of the pay-off reel towardthe first deposition station. The glow bars prepare the substrate toassist in adhesion of material that will be deposited.

The substrate is then drawn toward the first deposition station toreceive a first layer of material. For purposes of this example, a 200 Ålayer of ITO is provided by PVD means, specifically a sputtering processprovides the thin film materials to be deposited upon the substrate.Material provided by the sputtering process is confined within adeposition region adjacent to the first deposition station. For purposesof this example, the substrate is continuously moving, although oneskilled in the art would immediately recognize that the teachings of thepresent disclosure are not bound to a continuously moving substrate.

One advantage of the present invention is that the material which isrequired for the stack design is provided without being exposed toexternal influences. In the instant example, the background gas withinthe deposition chamber is argon. If the substrate was removed from thedeposition chamber after the first layer of Si was deposited, then thelayer would be exposed to oxygen and other external influences.Oxidation would be apparent upon the surface of the Si layer. Bydepositing the entire stack within a deposition chamber, materialproperties are maintained and impurities that may otherwise form on theexposed surface of the various deposited layers are prevented.

The portion of substrate having received the first layer is then drawnto a second deposition station, where a second layer is provided uponthe substrate by either PVD means, or CVD means. In this example, a 200Å layer of SiO_(x) is provided by PVD means, specifically a sputteringprocess. The material provided by the sputtering process is confinedwithin a deposition region located adjacent to the second depositionstation. The portion of substrate having received the second layer isthen drawn to a third deposition station, where an 800 Å layer of ITO isprovided by a sputtering process. Non-deposited species provided by thesputtering process are confined within the deposition region as with thefirst and second layers.

The portion of substrate having received the third layer of material isthen drawn to a fourth deposition station, where a 1000 Å layer ofSiO_(x) is provided by CVD means, specifically a MPECVD process.Containment of silane is critical at the fourth deposition station.Otherwise, silane molecules coming into contact with the ITO sputteringtarget would contaminate the ITO target.

The substrate having received all of the layers required for the stackdesign, is then drawn toward the take-up reel. The roll of completedmaterial is removed from the apparatus and prepared for shipping.

Selective solar radiation control coatings can be used to address thefull potential market for SSRC coated glass, especially in southernclimates. The instant coatings are made practical by low pressure, highdeposition rate microwave plasma enhanced chemical vapor deposition(PECVD) processes which are more economical than PVD process asdisclosed above. SSRC coatings, using only moisture resistant dielectricand/or semiconductor coatings are deposited in layers upon whateveroptical substrate is desired, typically glass or polymer, to form a typeof interferometer stack known as an optical stack. The optical stack isdesigned to absorb as much UV radiation as possible, reflect as muchnear IR radiation as possible and transmit as much visible light aspossible.

One particularly good combination of materials for production of anoptical stack is a Si₃N₄ (silicon nitride) dielectric and an amorphoussilicon semiconductor with added carbon to increase the band gap, SiC(silicon carbide). Unfortunately, the state of the prior art does notprovide a high speed, low cost method for production of such an opticalstack over a wide area, such as a window for commercial building. Theprior art provides a sputtering process at a rate of 10 angstroms persecond for silicon nitride and less than 5 angstroms per second forsilicon carbide. This would require a sputtering machine approximatelyin order of magnitude longer, and thus the process would be moreexpensive than to provide ZnO/Ag coatings. However, the widened MPECVDdevice disclosed herein makes these coatings economical.

Of great importance is the fact that these SSRC coatings contain nomoisture sensitive dielectrics (such as ZnO) or free metals which aresusceptible to oxidation (such as silver). Consequently, these coatingsdo not need to be placed in an inert gap of insulating glass unit.

In northern climates, the optimal SSRC device would have differentproperties in the winter than in the summer. In these climates, it isdesirable to reflect (or absorb) the UV and reflect the far IR in boththe winter and the summer. However, in the winter it is desirable totransmit the near IR to reduce heating costs. While in the summer, it isdesirable to reflect the near IR to reduce cooling costs. The durabilityand low costs of these SSRC stacks would enable the design of windowswear as coating mounted on a clear, flexible plastic substrate. It couldtake the form of a window or a shade or blind.

The band gap of a dielectric or semiconductor is the amount of energyrequired for an electron to transit from the valance band to theconduction band. The significance of the band gap in selective solarradiation control coatings is the correlation between wave length andenergy, expressed in electron volts of light. For example, the centerfrequency of visible light has a wave length of approximately 5500angstroms, which is equivalent to 2.2 electron volts. The band gap of adielectric or semiconductor will determine whether a given frequency oflight will be absorbed. The energy of light at a particular frequency iscommonly referred to as the photon energy. A photon energy greater thanthe band gap energy wilt result in absorption. Therefore, it isnecessary to express materials in relation to their and gap.

One embodiment of a selective solar radiation control coating of theInstant invention is one formed from a silicon carbide layer disposedbetween a first and second silicon nitride layer. The silicon carbidelayer has a band gap of about 2.0 eV or higher and is between about 500and 700 angstroms thick. This silicon carbide layer absorbs essentiallyall of the UV radiation. The first and second silicon nitride layerseach have a refractive index of about 1.9 or higher and are betweenabout 100 and 300 and 300 and 500 angstroms thick, respectively.

This silicon nitride/silicon carbide SSRC coating absorbs nearly all ofthe UV, reflects about 40% of the IR, and transmits over 86% of thevisible light. The transmission peak is centered around the center ofthe spectrum to which the human eye is sensitive; consequently, makingthe coating appear colorless. The thickness of the coatings and the bandgap of the SiC coating can be adjusted to fine tune the position andshape of the transmission curve, which adjusts the coating for colorneutrality.

Another embodiment of a selective solar radiation control coating of theinstant invention is one formed from a silicon carbide layer disposedbetween the first and second diamond-like carbon layer. The siliconcarbide layer has a band gap of about 2.0 eV or higher and is betweenabout 300 and 450 angstroms thick. The first and second diamond-likecarbon layers each have a refractive index of about 2.3 or higher andare between about 200 and 350, and about 400 and 500 angstroms thick,respectively.

This diamond-like/silicon carbide SSRC coating absorbs nearly all of theUV, reflects about 40% of the IR and transmits about 94% of the visiblelight. The transmission peak is centered around a portion of thespectrum to which the human eye is sensitive, consequently, making thecoating appear colorless. The thickness of the coatings and the band gapof the SiC coating can be adjusted to fine tune the position and shapeof the transmission curve, which adjusts the coating for colorneutrality.

Yet another embodiment of a selective solar radiation control coating ofthe instant invention is one formed from one or more dual layeredcoatings of silicon oxide and silicon nitride deposited upon thesubstrate. The silicon nitride layer is deposited adjacent to thesubstrate and if more than one dual layer coating is applied, thesilicon oxide and silicon nitride alternate. The silicon oxide layershave a refractive index of about 1.48 and are typically between about1100 and 1900 angstroms thick, and the silicon nitride layers have arefractive index of about 1.97 and are typically between about 1000 and1500 angstroms thick.

These dual layered silicon oxide/silicon nitride SSRC coatings absorbnearly all of the UV, reflects about 21% of the IR for one dual layer,45% of the IR for two dual ayers and 63% of the IR for three dual layersand transmit about 94% to 95% of the visible light. The transmissionpeak is centered around the portion of the spectrum to which the humaneye is sensitive; consequently, making the coating appear colorless.

These coatings are useful for forming coated optical articles whichinclude an optical substrate having at least one surface and at leastone selective solar radiation control coating deposited onto the opticalsubstrate. The optical substrate may be glass or plastic.

Yet another embodiment of a selective solar radiation control coating ofthe instant invention is one formed from one or more dual layeredcoatings of silicon oxide and titanium oxide deposited upon thesubstrate. The titanium oxide layer is deposited adjacent to thesubstrate and if more than one dual layer coating is applied, thesilicon oxide and titanium oxide layers alternate. The silicon oxidelayers have a refractive index of about 1.45 and are typically betweenabout 250 and 1260 angstroms thick, and the titanium oxide layers have arefractive index of about 2.30 and are typically between about 400 and1160 angstroms thick.

Some dielectric materials useful for the SSRC coatings of the instantinvention are silicon nitride, silicon oxide, titanium oxide, siliconoxynitride, alloys of these materials with carbon and diamond-likecarbon. Additionally, while silicon carbide has been disclosed as asemiconductor material, other materials such as silicon, doped silicon,germanium, doped germanium and germanium carbide are usefulsemiconductors.

While the invention has been described in connection with preferredembodiments and procedures, it should be understood that it is notintended to limit the invention to the described embodiment andprocedures. On the contrary, it is intended to cover all alternatives,modifications and equivalents which may be included within the spiritand scope of the invention as defined by the claims of appended hereto.

What is claimed is:
 1. In a microwave deposition device of the typehaving an applicator for producing a plasma and at least one microwavesource in communication with the applicator for providing microwavesthereto, the improvement characterized by: the applicator comprising afirst portion for receiving and transmitting microwaves and a secondportion for receiving and transmitting microwaves, wherein microwavesentering the first portion are prevented from entering the secondportion and microwaves entering the second portion are prevented fromentering the first portion.
 2. The microwave deposition device of claim1 wherein the first portion and the second portion each have a pluralityof apertures for radiating microwaves, the apertures ascending in sizealong each corresponding portion.
 3. The microwave deposition device ofclaim 1 wherein the microwave source is a single microwave source incommunication with both the first portion and the second portion.
 4. Themicrowave deposition device of claim 1 wherein the first portion andsecond portion are mirror images of each other.
 5. The microwavedeposition device of claim 1 wherein the first portion and the secondportion have opposed ends for receiving microwaves.
 6. The microwavedeposition device of claim 1 wherein the first portion and secondportions are separated by a shield.
 7. The microwave deposition deviceof claim 1 wherein the applicator is at least 120 centimeters long. 8.In a microwave deposition device of the type having a microwave sourceand an applicator, the improvement characterized the applicatorcomprising: a first portion and a second portion in close proximity toone another, each of said portions adapted to receive and transmitmicrowaves, each portion having an independent input for microwaves,wherein microwaves entering the first and second portions are preventedfrom traveling into the other of the first and second portions.
 9. Themicrowave deposition device of claim 8 wherein the first portion and thesecond portion each have a plurality of apertures for radiatingmicrowaves to form a plasma, the apertures of each portion ascending insize along each corresponding portion.
 10. The microwave depositiondevice of claim 8 wherein the first portion and the second portion eachhave a length greater than a width and are disposed end to end withopposed ends for receiving microwaves.